Dental restorations such as dental crowns and bridges are generally made using a metallic framework coated with a fused dental porcelain to provide the desired aesthetics. Today, however, there is an increasing tendency to use non-metallic materials for this purpose, particularly high strength porcelains which provide a more natural translucency and therefore, much improved aesthetics. These porcelain materials exhibit coefficients of thermal expansion much lower than the dental alloys used in porcelain-fused-to-metal applications, e.g., 5-8.times.10.sup.-6 as compared to 13-14.times.10.sup.-6 (room temperature to 500.degree. C.) parts per million (ppm) per .degree.C.
Accordingly, it is the object of the present invention to provide dental porcelain compositions which mature at a temperature consistent with the thermal stability temperature of ceramic cores and are chemically and thermally stable.
It is another object of the present invention to provide porcelain compositions which form a chemical bond with all-ceramic cores and which have a thermal expansion value of about 1 to 1.5 ppm per .degree.C. less than the expansion of the core which places the porcelain in slight compression when the fused restoration cools to room temperature.
It is yet another object to provide improved all-ceramic dental restorations.